1. Field of the Invention
The invention relates to the preparation of olefin sulfonates and more particularly pertains to an improved process for producing olefin sulfonic acids and sulfonates of improved low oil content and low color from mixtures of olefins having 14 to 16 carbon atoms per molecule which contain at least 30 percent by weight dimer olefins.
2. Description of the Prior Art
Processes for producing olefin sulfonic acids and olefin sulfonates by the use of continuous falling film reactor apparatus are well known in the art. Generally, conventional continuous falling film reactor apparatus comprise a vertical reaction zone surrounded by a suitable heat exchange means, and include means for forming a continuous falling thin film of olefin product in the reaction zone and a means for injecting sulfur trioxide into the reaction zone. The thin continuous falling film of the olefin to be sulfonated is formed in the reaction zone and sulfur trioxide, with a gaseous diluent, is mixed and reacted therewith. The sulfonation reaction which occurs is normally highly exothermic, depending upon the particular olefin utilized, resulting in an olefin sulfonic acid reaction product or effluent. Through the use of the heat exchange means, the exothermic reaction temperature can be substantially controlled, thereby retarding degradation of the acidic reaction product which produces off-color and other undesirable problems. Examples of prior art processes for preparing olefin sulfonates by the use of continuous falling film reactor apparatus are disclosed in the following U.S. Pat. Nos.: 3,169,142; 3,501,276; 3,420,875; and 3,461,053.
There are, of course, several variations known in the art of the above-described somewhat conventional process and apparatus for the production of olefin sulfonic acids and sulfonates. For instance, Brooks teaches in U.S. Pat. No. 3,620,684 an improved process and apparatus for continuous sulfonation of olefins wherein the acidic reaction product of an olefin and sulfur trioxide mixed and reacted in a reaction zone is immediately cooled after passing from the reaction zone, to retard degradation thereof. The preferred method of cooling disclosed is a recycle-quench step of the acidic reaction product which aids completion of the sulfonation reaction.
However, attempts heretofore to produce olefin sulfonic acids and sulfonates of low oil content and low color from olefin feed mixtures having 14 to 16 carbon atoms per molecule wherein at least 30 percent by weight of the mixtures are dimer olefins have been substantially unsuccessful, particularly at acceptable production rates. The acidic reaction products or effluent from the above-described C.sub.14 -C.sub.16 dimer olefin mixtures mixed and reacted with sulfur trioxide are highly thermally sensitive. On the other hand, the sulfonic acid and sulfonate products prepared from C.sub.14 -C.sub.16 dimer olefin mixtures are highly desirable for use in preparing light duty liquid detergents which are biodegradable. In the preparation of these products by prior art processes, the production rate is normally quite low and additional treatment steps are usually required to lower the oil content and off-color.
Another disadvantage in the use of known prior art processes and apparatus for preparing olefin sulfonic acids and sulfonates from the above-described C.sub.14 -C.sub.16 dimer olefin mixtures is the concurrent production of off gas plumes that are most difficult to treat for air pollution abatement. Tests have shown that these off gas plumes include not only inert diluent gas and unreacted sulfur trioxide but also large amounts of the sulfonic acid reaction product in aerosol form. Hence, expensive pollution abatement devices must be utilized, e.g., alkaline scrubbing devices, after burners and the like, before the off gas plume can be released into the atmosphere.